Survivors and relatives of those who lost their lives in the 2002 Bali bombings have gathered on the island to commemorate the 10th anniversary of the worst terrorist attack on Indonesian soil.

A total of 202 people from 21 nations, including 28 Britons, were killed on October 12, 2002 when the al Qaida-linked Jemaah Islamiyah group launched terror attacks on two Bali nightspots packed with tourists.

Threats of a repeat attack on the 10th anniversary prompted a high security presence at the ceremony, which was attended by Indonesian foreign minister Marty Natalegawa, as well as Australian prime minister Julia Gillard, and John Howard, who was the country's leader at the time of the attacks. Among the dead were 88 Australians. Ms Gillard spoke of the "searing pain and grief" caused by the attacks.

More than 2,000 police and military, including snipers, guarded the service after authorities raised security alerts to their highest level after receiving intelligence of a terrorist threat to the ceremony. During the service a row of photographs of the victims was displayed and each person's name was read, while candles were lit to represent each of the nations that lost people.

Memorial services were also held across Australia to mark the anniversary, and a closed ceremony will be held in London where more than 100 relatives and friends of British victims will mark the 10th anniversary.

At the ceremony, at the Bali bombings memorial near St James's Park, family members and friends will be joined by diplomats from other countries that lost people in the bombings, as well as Foreign Office minister Hugo Swire. There will be a wreath-laying ceremony as well as a two-minute silence. Relatives of the 28 British victims have also organised a service at St Paul's Church in Covent Garden. They have said they want to see a final push to make sure those responsible are held to account.

Susanna Miller, whose brother Dan, 31, died in the attacks, while his wife Polly was badly burned, called for open justice for Hambali, claiming his nine-year detention without charge by the US is an "open travesty of human rights". She said: "We find ourselves in this slightly curious position of fighting for the rights of one of the people responsible for the deaths of our relatives."

The 45-year-old, who lives in north London, visited the Foreign Office last week to discuss the issue and a spokesman confirmed it is being looked into. She said many relatives had not travelled to Bali for the anniversary because of security concerns.

In a statement, Prime Minister David Cameron said: "A decade ago today in Bali, one of the most horrific terrorist attacks in history claimed the lives of 202 innocent people from 23 countries, including 28 from Britain. As the London memorial states, they were robbed of life, but their spirit enriches ours. Our thoughts remain with their families on this tragic anniversary.

"Just like 9/11 in America and 7/7 in London, the attack on Bali was an attack on us all. It taught us just how the security of our countries is now so inevitably intertwined. But it also showed us that we can and must stand together, united against those who threaten our way of life with extremist attacks. In the 10 years since that terrible day, Indonesia, the most populous Muslim population on the planet, has firmly rejected extremism and shown us all that religion and democracy can live side by side."